Dichotomous table for gallers on Chrysanthemum

(incl. Argyranthemum, Coleostephus, Dendranthema, Leucanthemum, Leucanthemopsis, Parthenium, Pyrethrum, Tanacetum pp.)

by Hans Roskam

1a On above-ground upper plant parts => 6

1b On roots, rhizomes or root collars => 2

2a On root collar, rhizome or subterranean buds => 3

2b Roots with small nodule-shaped swellings. Chrysanthemum spp.: Meloidogyne hapla

3a Considerable proliferations on the root collar => 5

3b On rhizome buds or rhizomes => 4

4a Rhizomes with rotund swellings, up to 5 mm long, succulent, containing one or several chambers. A white larva develops in each chamber. Leucanthemum vulgare, Tanacetum corymbosum: Oxyna nebulosa

4b Stem of the upper root part, especially the basal buds, thickened; rosette stunted; leaves swollen to a uniform fleshy gall, remaining closed; ± covered by stunted leaf parts. Larva reddish. Leucanthemum atratum, L. vulgare: Rhopalomyia hypogaea

5a Crop-like proliferations, globular, usually uniformly, with compact rough surface. Chrysanthemum spp.: Agrobacterium tumefaciens

5b Ramification of root collar. Shoots only stub-shaped, irregular, partially even leaf-like broadened, fleshy thickened; forming ± dense witches’ broom-like clusters composed of markedly degenerate leaves. Chrysanthemum spp.: Rhodococcus fascians

6a Galls on capitula, flowers or fruits => 28

6b Malformations of vegetative plant parts, occasionally also protruding parts of, or complete inflorescences => 7

7a Malformations exclusively, or predominantly, on leaves or apical shoots => 12

7b Malformations mainly on stems, sometimes additionally also on the petioles and leaf veins => 8

8a The inducers are inside the galls => 9

8b Stem over various lengths ± bulged, swollen, occasionally curled. On the rind some to many, wall-like framed depressions containing a flat scale insect. Leucanthemum vulgare: Planchonia arabidis

9a Malformations ± expanded, however with locally distinct solitary galls => 11

9b Malformations of different dimensions, without distinct solitary galls => 10

10a Stem slightly swollen close to the inflorescence, somewhat stunted and more pubescent. In the hollowed pith is a caterpillar, which often also ± infests the receptacle. Leucanthemum vulgare: Unidentified lepidopteran

10b Stem mainly underneath the flower head differently malformed, often over extended length, spongy, swollen, partially screw-like curled or curved. Neighbouring capitula stunted and deformed to a different extent. Leucanthemum: Ditylenchus dipsaci

11a Stem internodes ± stunted and swollen, occupied often with many, 2–3 mm long, acute-conical, ± obliquely protruding, ± pubescent galls. Corresponding galls often simultaneously also on leaves and sometimes axillary buds and even galling parts of the inflorescence. Hosts in case of severe infestation often largely deformed. Larvae initially milk-white, yellowish to red-orange later on. C. indicum, rubellum, incl. various forms: Rhopalomyia chrysanthemi

11b Similar malformations of stem and buds with usually less many fleshy galls. One reddish larva per gall chamber. Leucanthemum vulgare etc.: Rhopalomyia hypogaea

12a Wart-shaped, distinctly defined swelling caused by fungi, hardly 1 mm long or ± flat callous, which fruit either in the inside or on the surface of the galls => 24

12b Leaves with strongly protruding swellings, flat, ± irregularly bordered or with expanded marginal rolls and curls, usually caused by animals => 13

13a Leaf blades with malformations of various shape and growth, usually on several terminal leaves; caused by aphids, cercopids, leaf-hoppers or erineum-like fruiting fungi => 20

13b Leaves with locally restricted malformations, often many or with narrow rolls => 14

14a Conspicuous malformations of the leaf margin => 18

14b Malformations of the leaf blade => 15

15a Leaf blade with succulent, conical, or nodule- to bulge-like galls => 16

15b Leaf blades predominantly of the rosette leaves, with many dimple-shaped swellings, protruding on the upper side. Leucanthemum vulgare: Trioza chrysanthemi

15c Similar dimples on the basal leaves containing froth-covered nymphs. Leucanthemum vulgare: Craspedolepta flavipennis

15d Slightly locally suberose leaf swellings. Thrips nigropilosus

16a Galls up to 3 mm long, conical or nodule-shaped => 17

16b Petioles, usually of several rosette leaves, shortened, markedly spongy, swollen, pale green. Swellings variously extending into the leaf blade; sometimes ± isolated on the leaf blade and fading from a rugose vein into the leaf blade, again conspicuously pale green. Leucanthemum maximum: Ditylenchus dipsaci

17a Leaf blade with nodular swellings, Tanacetum corymbosum: Unidentified eelworm

17b Leaves often with many conical galls, on the upper side or also beneath, obliquely protruding, 2–2.5 mm long. Corresponding lumps often simultaneously on other plant parts. Larvae initially milk white, later red-orange. C. indicum: Rhopalomyia chrysanthemi

18a Leaf blade margin lacerate => 19

18b Leaves with downward rolls. Tanacetum corymbosum: Unidentified psyllid

19a Leaf blade lacerate, with small protrusions on the upper side. Leucanthemum vulgare: Unidentified gall mite

19b Leaf blade deeply and irregularly striped, long white pubescent. Tanacetum corymbosum: Cause unknown – ? gall mite

20a Leaf blade bent and curled by animal parasites => 21

20b Leaves usually with several shoot tips locally or completely bleached, swollen, ± curved or deformed in other ways; the underside soon covered by a coherent dirty violet fungus. Capitula, if present, severely stunted, sometimes with hardly spreading, shortened and greened ligules and likewise ± greened tubular florets. C. segetum: Peronospora danica

21a Malformations by aphids => 22

21b Leaves nest-like contracted, close to the site of attack curled, dark green. Infestation of stem leaves or stems often leads to curved, one-sided thickened stems with converged, ± rolled leaves. Infestation of stem parts close to the capitula results in diverse malformations on inflorescences and flowers. Chrysanthemum spp.: Philaenus spumarius

22a On Leucanthemum vulgare, Tanacetum corymbosum => 23

22b On Chrysanthemum indicum, Argyranthemum frutescens. Leaves and also flower parts deflected. Aphids dark browns to black. 1.5–2.5 mm long, antennae as long as body, siphunculi thick, conical, slightly shorter than the long cauda: Macrosiphoniella sanborni

22c Superior internodes strongly shortened, with dense tufts of leaves and stunted capitula. Argyranthemum frutescens: Macrosiphoniella artemisiae

= Various malformations of shoot- and inflorescences may be virus-associated.

23a Leaf blade of Leucanthemum vulgare deformed by green aphids, curved. Attack on terminal shoots results in considerable stunting and curling of plant parts, incl. capitula and flowers. Aphid about 2–2.3 mm long and with almost black siphunculi: Brachycaudus cardui

23b In similar malformations on several Chrysanthemum species occurs another aphid, which is only 1.5–2 mm long with green to olive-brown siphunculi: Brachycaudus helichrysi

23c Basal leaves of Tanacetum corymbosum curved, soon yellowing: Macrosiphoniella miestingeri

24a Sori cushion- or bulge-shaped; fruiting bodies at the surface, on Leucanthemum vulgare => 27

24b Galls wart- or pock-like with spores inside => 25

25a Galls nodule-shaped, over 1 mm wide => 26

25b Underside of the rosette leaves often with many, hardly 1 mm long hemispherical, pearl-like warts, with a yellowish translucent fungal body. in the middle. Leucanthemum vulgare: Synchytrium aureum

26a Usually distinct, rotund, flat pocks up to about 2 mm long, initially grey-white, later browned, predominantly solitary; mostly with several on the underside of basal- as well as stem leaves; more rarely on petioles or stems. Spores of various size, thick-walled; terminally produced on the mycelium ramifications, outside the vascular bundle. Leucanthemum vulgare: Protomycopsis leucanthemi

26b Similar, mostly less conspicuous flat, initially whitish-yellow pocks on the leaf underside, sometimes also on the stems of the inflorescences. Leucanthemopsis alpina: Protomycopsis leucanthemi

27a Underside of the rosette leaves mostly with many, small, rotund, brown telia; if produced on petioles of young leaves in especially early spring sometimes slightly swollen, mostly yellow-margined, oblong-oval cushions. No host alternation: Puccinia leucanthemi

27b Leaf underside with rotund, 3–10 mm wide yellowish, often purple-margined aecia. Sori on main veins sometimes slightly bulge-like swellings. Species alternating on Carex montana: Puccinia aecidii-leucanthemi

27c Similar aecia, on the same host but alternating on Carex caryophyllea, ericetorum: Puccinia leucanthemi-vernae

28a Galls mainly locally in capitula, on the receptacle, involucre, bracts or fruits => 35

28b Malformations over ± extensive parts of the inflorescence => 29

28c Slight swelling of main stem below flower head, causing distortion of head, with side shoots growing past it; larva tunnels inside stem and often into flower head from which frass may exude, in stem or head (or in ground). Leucanthemum vulgare: Dichrorampha consortana

29a Malformations of approximately well-defined shape, involving the receptacle => 33

29b Malformations of varying extensions on parts or complete capitula => 30

30a Malformations of ± open capitula => 32

30b Capitula stunted, remaining closed => 31

31a Capitula slightly swollen; several yellow to pink jumping larvae between the achenes. Leucanthemum vulgare, maximum: Contarinia chrysanthemi

= The gall midge Dasineura chrysanthemi has been recorded from flower heads of Leucanthemum vulgare; as well midge larvae assigned to Jaapiella sp.

31b Complete flower head deformed, flowers aborted. Leucanthemum vulgare: Paraphytoptus chrysanthemi

= For the ornamentally cultivated C. carinatum, indicum, conspicuous damage caused by viruses has been recorded. Malformations consisting of greening of the flowers in connection with malformations of the capitula

32a Malformations caused by aphids or cercopids => 21

32b Inflorescence variously stunted or deformed; infected organs partially covered with an area of loosely, dichotomous, grey-violet conidiophores. Tubuliform flowers often soon withered, infected ligules elongated, often variously curved, usually with abundant oospores, lacking conidiophores. Leucanthemum vulgare: Peronospora radii

33a Receptacle swollen, without involvement of the often strongly atrophied flowers => 34

33b Receptacle locally, including one or several flowers, initially swollen to a succulent, conical, apically almost closed gall, surmounting the later ± deformed disc. One reddish larva. Leucanthemum vulgare: Rhopalomyia hypogaea

= Similar galls but with terminally spreading lobes later on Leucanthemum vulgare are caused by the gall midge Rhopalomyia tanaceticola which lives usually on Tanacetum.

34a Receptacle deformed, ± swollen, hardened. Leucanthemum vulgare: cf. Eurasimona stigma

= According to Smit (2010) the capitula of Leucanthemum vulgare are also infested by the tephritid fly Tephritis neesii; widely distributed in Eu, no records from E-Eu.

34b Receptacle almost only enlarged in combination with corresponding swellings on the neighbouring parts of the stem and accordingly curved. Leucanthemum vulgare, maximum: Ditylenchus dipsaci

35a Up to 2 mm long, obliquely protruding, conical galls on leaves of the involucre and solitarily scattered even on the ligules. C. indicum: Rhopalomyia chrysanthemi

35b Ovary or fruit swollen without or together with the lower flower parts. Also the bract may be involved in the gall formation. One yellow larva. Chrysanthemum argenteum (Tripleurospermum inodorum and Anthemis bornmuelleri are main hosts; furthermore Leucanthemum vulgare: Ozirhincus longicollis

35c Similar galls; Chrysanthemum coronarium, segetum: Ozirhincus anthemidis

= O. longicollis and O. anthemidis differ by the length of the adult proboscis: in O. longicollis proboscis long, from base of labrum to tip of labella longer than height of eye; in O. anthemidis proboscis shorter than height of eye.

mod 27.xi.2019